Stabilizers for stabilizing the steering linkage of a vehicle while yieldibly biasing the vehicle wheels toward a straight-ahead direction have been known for some time. Prior art stabilizers typically comprise a fluid damped shock absorber yieldibly biased by one or more biasing springs to an intermediately extended position. The stabilizer usually is connected between a movable portion of a vehicle steering linkage and a fixed portion of the vehicle frame with the straight ahead direction of the vehicle wheels corresponding to the spring biased intermediately extended position of the stabilizer. When the vehicle wheels have been turned resulting in an extension or contraction of the stabilizer and the turning force is removed or dissipated the biasing spring or springs tend to return the stabilizer to its biased position and consequently the wheels to their straight-ahead direction.
Prior art stabilizers, while useful, have several shortcomings. Dual spring stabilizers such as those exemplified in U.S. Pat. Nos. 1,745,117 of Plank, 3,980,315 of Hefren, and 4,406,473 of Sexton may sometimes produce an uneven steering response or recovery because the springs do not have precisely the same spring tension especially after extended use. In addition, dual spring stabilizers are relatively expensive to produce. Prior art single spring stabilizers such as those illustrated in U.S. Pat. Nos. 3,464,688 of Papousek and 3,951,391 of Papousek have a single spring that is compressed upon the vehicle wheels being turned in one direction and extended upon the wheels being turned in the other direction. These stabilizers also result in uneven steering response and recovery because the recovery force of a compressed spring is not the same as its recovery force when expanded. In addition, the single spring does not provide strong biasing forces at the biased position because the spring is under neither tension nor compression when the stabilizer is in that position.
Thus, it can be seen that a steering linkage stabilizer that provides identical biasing forces in either direction, a strong positive biased position, and that is relatively inexpensive to produce would eliminate those problems of prior art devices and, hence, is highly desirable.